L1.Microbial Path Intro

Question 1

Distinguish between Colonization, Infection, and Disease?

Answer 1

Colonization: a bacterium enters a body, finds a niche and persists in the particular site.
Infection: A bacterium which is CAPABLE of causing a disease becomes established in the body.
Disease: Is an infection that produces symptoms.

Question 2

What is a PRIMARY INFECTION?

Answer 2

Infection caused by exogenous pathogens (an organism not normally found in healthy humans).
Note: also referred to as an EXOGENOUS Infection

Question 3

What is an OPPORTUNISTIC INFECTION?

Answer 3

An infection caused by generally “NORMAL FLORA.”

Note: Also referred to as an ENDOGENOUS Infection

Question 4

What are two problems that prevent Koch’s postulates from being useful in all cases?

Answer 4

1. Can’t culture all bacteria in lab

2. Sometimes can’t reproduce disease in Animal

Question 5

How is Koch’s Postulate changed in its MOLECULAR VERSION?

Answer 5

1. The disease should be significantly associated w/ a specific GENE found in the strains of bacteria that cause the disease.
2. Activating/Inactivating this GENE should increase/decrease the Virulence. Additionally, introduction of a cloned GENE into an avirulent strain should render the strain virulent.
3. GENE must be Expressed by bacterium when in human/animal with disease.

Question 6

Of the 4 major groups of microorganisms, Gram+ cocci & rods and Gram- cocci & rods, what are the two that most frequently cause human disease?

Answer 6

1. Gram Positive Cocci

2. Gram Negative Rods

Question 7

What type of bacteria is Mycobacterium tuberculosis? What disease does it cause?

Answer 7

It is an acid-fast bacteria that causes TB

Question 8

What disease does the bacterium Carynebacterium diptheriae cause? Through what mechanism is the disease contracted? Is it a threat in developed countries?

Answer 8

C. ditheriae causes Diptheria disease. Diptheria is an upper respiratory tract infection that is no longer a threat in developed countries due to well developed/effective vaccinations.

Question 9

What type and shape of bacteria is C. diptheriae?

Answer 9

A Rod (Club) shaped gram positive bacteria

Question 10

After a 2-6 day incubation period Diptheria expresses very similarly to a common cold. However, after awhile breathing obstruction, irregular heartbeat and coma may occur. What is the cause of the more serious affects of a C. diptheriae infection?

Answer 10

1. Breathing obstruction is caused by PSEUDOMEMBRANE FORMATION.
2. Irregular heartbeat and coma are caused by the Diptheria TOXIN (DT) produced by the C. diptheriae.

Question 11

How is toxic domain A of Dipetheria Toxin able to separate from the rest of the toxin after it is translocated accross the membrane by the T domain.

Answer 11

PROTEOLYTIC NICKING: the A and B domains are held together by a disulfide bond that is broken via a reduction reaction.

Question 12

What is the function of the B-domain of Diptheria Toxin (DT)? How could this be used in cancer therapies?

Answer 12

The job of the B-domain in DT is to bind to protein receptors on the outside of cell membranes and get the DT endocytosed into the cell. If you could get a B-domain that specifically targeted cancer cell you could deliver the toxic A-domain to cancer cells but not others.

Question 13

What are the 3 methods of treatment for Diptheria?

Answer 13

1. Anti-toxin antibodies made in horses (passive immunity).
2. Antibiotics - penicillin or erythromycin
3. Vaccination - DPT

Question 14

What portion of the DPT vaccine target C diptheriae bacteria? Is it effective?

Answer 14

The D part = Diptheria Toxoid - toxin inactivated with formaldehyde. Very Effective & safe. 4 shots b4 2 yr –> resistant for life

Question 15

Bordetella pertussis causes what disease? What is the type and shape of the B. pertussis?

Answer 15

B. pertussis is a small, GRAM-, strictly aerobic ROD that causes WHOOPING Cough.

Question 16

How is B. pertussis acquired? What type of infection occurs?

Answer 16

Inhalation –> respiratory infection.

Question 17

What are the main symptoms of whooping cough?

Answer 17

Repetitive coughing with ‘whoops’. Cough lasts for a very long time.

Question 18

What portion of the DPT vaccine treats whooping cough? What is potential problem with it?

Answer 18

The P portion = Pertussis - heat killed Bordetella pertussis. B/c it isn’t just the toxin and it is actually killed B. pertussis may cause minor fever and in very rare cases brain damage.

Question 19

How does B. pertussis avoid the immune defense of mucus and cilia removal?

Answer 19

B. pertussis binds specifically to Cilia with ADHESINS.

Question 20

What are the two Adhesins produced by B. pertussis? Describe briefly.

Answer 20

1. Filamentous Hemagglutinin (Fha) - forms filamentous structure on the cell surface.
2. Pertussin Toxin (Ptx) - Has 6 subunits (S1-S5 w/ 2 S4s).

Question 21

Describe the roles of the 6 Pertussin toxin (Ptx) subunits.

Answer 21

S2 & S3 mediate the binding
S4s provide conformational change and move S1 subunit into cytoplasm of cell
S1 is the toxic portion of Ptx.

Question 22

By what mechanism does the S1 subunit of Ptx cause toxicity?

Answer 22

S1 acts in a very similar manner to the A-domain of Diptheria toxin. It causes ADP ribosylation, modifying cellular proteins. But target is different. S1 targets a G-protein stopping the regulation of cAMP –> high levels of cAMP.

Question 23

What are the 2 methods of treatment of whooping cough?

Answer 23

1. Antibiotics - Doesn’t actually benefit patient but stops further infection and spread of pertussis to others. Erythromycin.
2. Vaccination - DPT